James R. Arnold, a University of California San Diego chemist who helped develop the radiocarbon dating technique that's widely used in archaeology and later analyzed some of the first moon rocks brought to Earth by the Apollo astronauts, died Jan. 6. He was 88.

Arnold, who also was founding chairman of the UC San Diego chemistry department and who directed the California Space Institute, passed away after a long illness, campus officials said.

"Jim Arnold truly was a visionary scientist who found creative ways of looking at a broad range of problems, terrestrial and extraterrestrial," Mark Thiemens, the university's dean of physical sciences, said in a statement.

Arnold was born on May 5, 1923, in Metuchen N.J., the son of a lawyer and archaeologist. He enrolled at Princeton University at 16 and earned his doctorate there, largely based on research that he conducted while working on the Manhattan Project, the successful effort to produce the first atomic bomb.

"His thesis is actually still secret," said Ken Arnold, one of his three children. "He never told us what it was about, but he said he didn't much mind because it was wrong. The atomic bomb brought him to a deep concern about world peace and nuclear war, and he was an early member of the Union of Concerned Scientists."

He then moved to the University of Chicago, serving as a post-doctoral fellow under the famed chemist Willard Libby. Arnold, a geophysical chemist, contributed to Libby's effort to develop radiocarbon dating, which revolutionized archeology and paleontology.

"I think one of the reasons (he gave me a position) was that my father was a very serious amateur in Egyptian archeology," Arnold told historian Spencer Weart. "He was American Secretary of the Exploration Society of London, which meant basically he was a fund-raiser for them, but I grew up with a library full of books on the subject and all that. And so I spoke the language, and I could appreciate immediately what an exciting project this was."

The breakthrough in carbon dating earned Libby the 1960 Nobel Prize in chemistry.

Arnold's tenure at Chicago was brief; he moved on to Harvard, where he was a National Research Fellow. Then he returned to Princeton in 1955, joining the faculty.

His return to Princeton also was brief. Arnold's research on cosmic rays and other areas of science caught the attention of Roger Revelle, who was looking for talented faculty for the newly planned UC San Diego campus. Arnold signed on in 1958 and became the founding chairman of the chemistry department two years later. He was in heady company; his colleagues at UC San Diego included Harold Urey who had won the Nobel Prize in chemistry for discovering heavy hydrogen.

Arnold recruited many faculty, an effort that, at times, proved relatively easy. His son Ken says, "In the beginning, the nascent USCD was on the grounds of Scripps Institute of Oceanography, and my father's lab had glass sliding doors just over the beach. That lab was one of his favorite recruiting tools. He would pick up a recruit at the airport and "have to" stop at the lab on the way home. He'd then tinker around the lab for a few minutes while the recruit ― usually from a colder place ― stood and stared out at the beach. For people from stuffy Eastern and Midwestern academia this often sealed the deal at the start."

His coups included recruiting Maria Goeppert Mayer from the University of Chicago. Ken Arnold says, "She had already done the science that would win her a Nobel prize, but as a woman the University of Chicago had only let her teach, unpaid. My father was the first to offer her a full professorship, at the same level offered to her also-accomplished husband (Joe). That recruitment was short and easy."

Arnold was soon splitting time between San Diego and the newly created National Aeronautics and Space Administration. Arnold became a key adviser on lunar exploration, and helped elevate the space agency's scientific research.

"When President Kennedy announced the lunar program, he stressed that his goal was to place men on the moon and return them safely to Earth," said Gerald Wasserburg, an emeritus professor of geology and geophysics at Caltech who worked with Arnold. "But Kennedy didn't say anything about the rocks that were to be returned. At first, those rocks were treated like souvenirs instead of scientific specimens."

The oversight led to the creation of the "Four Horsemen," an informal group that helped NASA establish protocol for the distribution and use of rocks returned from the moon. The group was made up of Arnold, Wasserburg, and researchers Bob Walker and Paul Gast. The "Horsemen" also pressured the government to keep the Apollo program going, a campaign that was not fully successful. Three planned moon landings were canceled, largely for budgetary reasons.

Arnold was more than an adviser during that period. He analyzed some of the first moon rocks brought to Earth, helping to refine the age and nature of the moon. His collaborators included Urey, then one of the best known scientists in the country.

Arnold, who often wore colorful shirts made by his wife, was following a deep passion. He would later tell the Los Angeles Times how inspired he had been early in life by such books as Jules Verne's, "From the Earth to the Moon."

"Jim went all Buck Rogers in later years; he wanted to colonize space," Wasserburg said. "I thought it was absurd. He told me it was important to do something grand, in whatever field you were working. I liked that about him."

UCSD says Arnold "is survived by his wife Louise Arnold, whom he met at a World Federalist conference in 1950 and married in 1952, and their sons Bob, Ted and Ken, and their families."